One of the frustrating things with working with spot colors in the past has been that the CMYK equivalents that Adobe products used, didn't match the equivalents that Pantone provided in their books. I've seen hints that with Pantone Plus, that may no longer be a problem. Does anyone know for sure whether the Pantone Plus color definitions will be consistent from CS products across the Pantone books?

The CMYK equivalents are derived from both the L*a*b values supplied by Pantone AND the CMYK profile you have loaded in your Color Settings CMYK Setup, so there are several variables to consider there. If you are using the same L*a*b values, CMYK profiles and rendering intent, your equivalents should be very close if not exact.

Adobe maintains this behavior to match legacy files. If they changed behavior now, then future outputs would change, and consequently new printings could look different from previous printings. This problem was encountered by Quark users with the change to version 7, when the Quark default switched from Solid to Process to Color Bridge Coated.

In previous post PDF mentioned Lab values, and that is the better way to convert Pantone colors to CMYK. But to do this you need to open the Ink Manager through the Swatches panel (in InDesign). Enable "Use Standard Lab Values for Spots". (note: Illustrator has a similar option, although it does not have an Ink Manager like InDesign). Notice that the CMYK icon changes to a Lab icon in the Swatches panel.

The conversion from Lab to CMYK is affected by the rendering intent and the Document CMYK color space. To see these, go to Edit: Assign Profiles.

If you have a spot color in InDesign, it is much better to make it process using the Ink Manager, instead of changing the color mode of the Swatch. If you need to convert one ink but not another, click on the spot icon in the Ink Manager to convert just one.

Regarding Pantone Plus: the Lab values of the spot colors have changed from the older Pantone libraries, along with the book CMYK values.

Edit: To see all the active inks in InDesign or Illustrator, use Separation Preview.